This project serves as the "chemistry component" of a comprehensive collaborative effort, the ultimate goal of which is to develop useful novel drug analogs which produce their effects by interacting with the newly discovered cannabinoid receptor(s). The proposed project will seek to develop novel covalent and non-covalent high affinity ligands for the cannabinoid receptor. These novel analogs will be used to obtain detailed information on the molecular features of the cannabinoid receptor sites and the manner with which the different cannabimimetic ligands interact with these sites. This will be accomplished by covalently labeling the active sites of cannabinoid receptor preparations which will be produced using recombinant methods. Information obtained from such work could lead to the development of a novel non-opioid analgesic devoid of psychotropic properties or a cannabinoid antagonist to counter the ill effects of cannabinoids. Analogs from four structurally different classes of cannabimimetic agents including, classical and non-classical cannabinoids, aminoalkylindoles and anandamides will be synthesized. The ligands are designed either as photoactivatable or electrophilic, irreversible probes or as high affinity reversible probes. Their conformational properties will be studied using high resolution NMR and computational methods. The biochemical and pharmacological testing of analogs will determine their usefulness as probes and as drug prototypes (agonists, antagonists) and will be carried out under the auspices of Core 2. The most promising analogs will be radioiodinated (Core 2) and used in experiments with preparations containing the cloned receptor or receptor mutants (Project 2) in order to determine the amino acid residues involved in the binding of each group of analogs in the cannabinoid receptor site (Project 3). The most promising reversible radioiodinated ligands will be used to study cannabinoid receptor distribution and the possible presence of new receptor subtypes (Project 3 and also collaboratively).